Light chain

Light chain refers to the smaller polypeptide subunit of an antibody (or immunoglobulin). Each antibody is made up of two types of chains: the larger heavy chain and the smaller light chain. Together, these chains form a Y-shaped molecule that is the basic structure of all antibodies.

Structure

The light chain of an antibody is composed of two identical proteins that are linked together by disulfide bonds. Each light chain has a variable region (VL) at one end and a constant region (CL) at the other end. The variable region of the light chain is involved in binding to antigens, while the constant region interacts with other parts of the immune system.

Types

There are two types of light chains in mammals: kappa (κ) and lambda (λ). These are encoded by different genes and can be distinguished by their different amino acid sequences. The ratio of kappa to lambda light chains varies among different species and in different types of immune cells.

Clinical significance

Abnormal production of light chains can lead to a number of diseases. For example, in multiple myeloma, a type of blood cancer, malignant plasma cells produce an excess of light chains, which can be detected in the blood and urine. This is known as Bence Jones protein.

In light chain deposition disease, abnormal light chains are deposited in tissues, leading to organ damage. In light chain amyloidosis, the light chains fold abnormally and form amyloid fibrils, which are deposited in tissues and can cause organ failure.

See also

• Heavy chain
• Immunoglobulin G
• Immunoglobulin A
• Immunoglobulin M
• Immunoglobulin D
• Immunoglobulin E